<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Text</title>
  <script>
    window.onload = function () {
      var body = document.body;
      // console.log(body);
      var text = body.firstChild;
      // console.log(text);
      console.log(text.length);
      text.appendData('asdfghjkl')
      console.log(text)
    }
  </script>
</head>

<body>
  hello world!!
</body>

</html>